The invention relates to a device for installation in a floating vessel intended for receiving a buoy or a turret in a submerged receiving space at the bottom of the vessel.
A device of this type is of current interest in connection with vessels for use in offshore production and/or transport of hydrocarbons, and especially vessels of the type having a submerged receiving space for the receipt and releasable securing of a socalled STL or STP buoy. These are buoys of the type comprising a bottom-anchored centre member and an outer buoyancy member which is rotatably mounted on the centre member and is conically upwards tapering and arranged to be received in a corresponding receiving space at the bottom of the topical vessel. An STL buoy is a buoy which is constructed for loading/ unloading, the abbreviation xe2x80x9cSTLxe2x80x9d standing for xe2x80x9cSubmerged Turret Loadingxe2x80x9d. An STP buoy is a buoy which is constructed for use in connection with a production vessel, the abbreviation xe2x80x9cSTPxe2x80x9d standing for xe2x80x9cSubmerged Turret Productionxe2x80x9d.
In connection with the development of the STL/STP technology it has become topical to use ships which are constructed or may be adapted to be used for several different applications, i.e. multi-purpose or MST ships (MST=Multi Service Tanker). Such ships may, for example, be used as shuttle tankers, the ships then being arranged to receive an STL buoy, or they mayxe2x80x94after a possible conversionxe2x80x94be used as production shipsxe2x80x94the ships then being arranged for receiving an STP buoy or a rotating body or turret which is dimensioned and adapted for the topical purpose.
When contracting and building such ships, it may sometimes be uncertain to which conditions of use or which field-specific requirements the ship in the first instance is to be adapted. This may then result in expensive postponements/delays before the ship can be finished, or it may become necessary to undertake expensive rebuildings/conversions for adaptation to the topical requirements.
On this background it is an object of the invention to provide a device which will enable quick and reasonable conversions of MST ships with short tender and decision terms.
Another object of the invention is to provide a device making it possible to avoid expenditures for building of receiving spaces and assembly of equipment for whichxe2x80x94at the building stagexe2x80x94one is uncertain whether it will be used.
For the achievement of the above-mentioned objects there is provided a device of the introductorily stated type which, according to the invention, is characterized in that it comprises a tubular body dimensioned for installation in a shaft extending vertically through the hull of the vessel and which, at its lower end, is arranged to receive a module unit provided with a through opening for receiving the buoy/turret, the module unit, when installed in the tubular body, at its lower end forming a seal against the tubular body, and at its upper end being fixed in relation to the tubular body by a locking means.
Apart from the fact that the solution according to the invention, which is based on the use of prefabricated module units, enables quick and reasonable conversions of MST ships, it also enables a quick and reasonable replacement of a module unit in case of changes in field-specific requirements to buoy or turret. A short conversion time will be a competition advantage in an FPSO market (FPSO=Floating Production and Storage of Oil) where the time from the commercial decision about field development is taken to the xe2x80x9cfirst oil on deckxe2x80x9d often is essential for the economy of the field.
In an advantageous embodiment of the device according to the invention the tubular body at its lower end is provided with a peripherally extending base which is conically downwards tapering, for the support of the correspondingly tapering portion of the module unit. The conically tapering base will provide for centering of the module unit in the tubular body and will also act as a force/weight distributor. Between the base and the tapering portion of the module unit there will be provided a sealing means which is to prevent water ingress between the body and the module unit.
By means of said locking means at the upper end of the module unit, the module unit can be fastened to the inner wall of the body, and thereby welding and burning in assembly/disassembly can be avoided. As a consequence of the fact that welding and burning are avoided, one can to a greater extent preassemble and finish equipment which is to be placed at the top of the module unit, while this is still not installed. This simplifies the installation procedure and makes this less vulnerable to delays as a result of unforeseen problems with functional tests, etc.